Tuned magnetic properties of Co-doped ZnO/B-doped graphene PN junction

Abstract

Co-doped ZnO(Zn1−xCoxO)/B-doped graphene(BG) PN junction with quasi-core-shell nanostructure is designed and fabricated by a facile chemical process. The interplay between the Zn1−xCoxO core and the BG shell is discussed. X-ray Photoelectron Spectroscopy (XPS) and photoluminescence (PL) spectra confirm that B and Co2+ ions are doped successfully. The C1s XPS spectra suggest the formation of the Zn(Co)OCO bonds, which can efficiently transfer the holes from BG to Zn1−xCoxO. X-ray diffraction (XRD) displays that Co doping hardly changes the wurtzite structure of ZnO. It can be clearly seen that edge of the BG covers Zn1−xCoxO to form the quasi-core-shell structure by High-resolution transmission electron microscopy (HRTEM). The position of the G band in Raman spectrum indicates that BG is P-type. The interaction between the Zn1−xCoxO and BG can be found by the red-shifts of E2H band of Zn1−xCoxO and broader 2D of BG as well. Magnetization measurement demonstrates that the increasing of the ferromagnetic phases in Zn1−xCoxO/BG nanoparticles with the increasing temperature. The observed ferromagnetic phases can be due to the exchange of the electron/hole at interface in the Zn1−xCoxO/BG PN junction.